Nitric oxide (NO) is a powerful signaling agent throughout the body. It is involved in a wide array of physiological functions, particularly those concerning blood flow. Because of its influence on vascular health, measuring nitric oxide levels has become a popular method for individuals and medical professionals to gain insight into overall cardiovascular function. This assessment helps determine the body’s capacity to produce this molecule, which is crucial for maintaining systemic health.
Why Measuring Nitric Oxide Matters
Nitric oxide is produced by the inner lining of blood vessels, known as the endothelium, and serves as a natural vasodilator. This means it signals the smooth muscles in the vessel walls to relax, causing the arteries to widen and allowing blood to flow more freely. This improved circulation helps regulate blood pressure and ensures oxygen and nutrients are efficiently delivered to all tissues and organs in the body.
Low levels of nitric oxide production are frequently associated with a condition called endothelial dysfunction, which is an early indicator of poor vascular health. When NO production is impaired, blood vessels may become stiff and constricted, contributing to issues like elevated blood pressure and a higher risk of heart problems. Measuring NO levels helps identify this deficiency early on, providing an opportunity to address the underlying causes through lifestyle or other interventions.
At-Home Salivary Testing
The most accessible method for the general public to check their nitric oxide status involves using non-invasive salivary test strips. These strips do not directly measure the unstable nitric oxide gas itself, which has a half-life of only a few seconds. Instead, they measure the concentration of its stable byproducts, nitrite and nitrate, in the saliva. Saliva is an effective proxy because the body’s conversion of dietary nitrates into NO begins with oral bacteria converting nitrate into nitrite.
To perform the test, a small pad on the strip is typically placed on the tongue for a few seconds or briefly dipped into a collected saliva sample. The pad contains a chemical agent, often based on the Griess reaction, which reacts with the nitrite present. This reaction produces a rapid color change on the strip, usually within 10 to 15 seconds.
The resulting color is compared to a calibrated chart on the product packaging, which corresponds to categories of NO availability, ranging from “Depleted” to “Optimal” or “Very High.” For the most accurate result, it is recommended to avoid using antiseptic mouthwash, eating, or drinking anything other than water before the test. These actions can temporarily disrupt the oral bacteria needed for the conversion process or dilute the sample. While convenient, these tests provide a snapshot of the dietary nitrate pathway and should not be considered a substitute for clinical diagnosis.
Clinical and Laboratory Measurement Methods
For a more precise assessment, clinical settings and research laboratories utilize advanced methods that measure nitric oxide metabolites in blood, urine, or breath. Blood plasma testing, often referred to as measuring NOx (nitrite and nitrate), estimates systemic NO production, although the instability of NO makes direct measurement difficult. Samples require careful handling and specialized preservation techniques to prevent the breakdown of metabolites before analysis.
Urinary testing offers a non-invasive way to quantify systemic nitric oxide metabolism by measuring the excretion levels of nitrite and nitrate. These samples provide insight into the body’s long-term NO status. A specialized method is the Fractional Exhaled Nitric Oxide (FeNO) test, which measures the amount of NO in the breath using a device that employs chemiluminescence.
The FeNO test is primarily used to evaluate airway inflammation, particularly in the diagnosis and management of asthma. Elevated levels of NO in the breath often correlate with inflammation in the lungs that responds well to certain medications. These clinical methods are significantly more precise than at-home strips, providing numerical data healthcare providers can use to establish a baseline or confirm a suspected diagnosis.
Interpreting Results and Normal Ranges
The interpretation of nitric oxide test results depends on the method used, but involves comparing the measured values against established reference ranges. For at-home salivary strips, the color change gives an immediate qualitative result, often displayed on a scale with categories like low, target, and high. A very light or absent color indicates low NO bioavailability, signaling a need for dietary or lifestyle adjustments.
Clinical FeNO results are measured in parts per billion (ppb) and have specific cut-off points, especially in adults. A value below 25 ppb is considered normal, suggesting minimal airway inflammation. Intermediate results range from 25 to 50 ppb, requiring further clinical context for interpretation. A FeNO result above 50 ppb is considered high, often indicating active airway inflammation related to conditions like allergic asthma.
A low result from any test is not a diagnosis but an indicator of suboptimal vascular function or inflammation. A low reading should prompt a consultation with a physician, who can order comprehensive blood panels to evaluate endothelial function and cardiovascular risk factors. Lifestyle factors like poor sleep, chronic stress, and a diet low in nitrate-rich vegetables can acutely depress NO levels, so results must be viewed in the context of daily habits.